string composition from form fields

[leian7]

For #77 . Needed for osuosl-pelican's https://github.com/osuosl/osuosl-pelican/issues/159

Changes

• [x] handles a form's fields_to_join as described in #77 when it is provided
• [x] adds another test similar to the existing test for format_message that includes a fields_to_join in the dummy POST request
• [x] validates the fields_to_join field if it exists

To run tests

• make tests

To "send" a test email (unable to send actual email locally because it would require running a local smtp server)

• in request_handler.py, comment out lines 467-481 and uncomment print(msg_send) on 466 instead
• Prepare your own test form with a hidden fields_to_join or use the premade example in templates: navigate to templates/ and do python -m SimpleHTTPServer [port num that isn't 5000]. Make sure your form action is to localhost:5000. You can also try including a nonexistent field in fields_to_join to test validation (see below for sample output).
• make run in another terminal
• got to localhost:[the port num your form is on] in your browser and submit the form. Verify that your fields_to_join were concatenated correctly if you supplied valid fields. Sample terminal output for index.html is below.

Expected output

• Tests pass (47)
• Test good "email":

  
  (venv) leian@turquoise:~/formsender$ make run
  python request_handler.py
  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
  * Restarting with stat
  From nobody Fri Jun  2 16:37:48 2017
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  Subject: Form Submission
  To: support@osuosl.org

Contact:

NAME: Firstname Lastname EMAIL: firstlast@example.com

Information:

firstlast@example.com:Firstname Lastname

127.0.0.1 - - [02/Jun/2017 16:37:48] "POST / HTTP/1.1" 302 -

- test bad "email": the email will not print in the terminal. The redirected page upon submission should include something like ?error=3&message=Improper+Form+Submission in the url.

Notes
- Did everything in ``request_handler.py``'s existing ``format_message`` method, but I can make a new method for ``format_message`` to call if needed. 

[ramereth]

@leian7 did you see my update to #77 related to this PR?

[leian7]

@ramereth I did, I discussed it with @Kennric , and my understanding is that the list provided to fields_to_join can be completely arbitrary; the form author gets to decide their specific string and its order. For extra bits like ibm-power they can have it be a hidden field. Is this correct? Or did you want $username:$user_first:$user_last:$phone:$company:$date:$email:ibm-power:support to always be included in the string?

[ramereth]

How will the date field work since it's not a field in the form?

[Kennric]

@leian7 @ramereth for the date, we'll need to calculate that - my thought was that we'd do it in the form, but on second thought I'd rather not add javascript for that. Let's have formsender check the fields_to_join list, and if it contains 'date' just insert today's date.

[ramereth]

@Kennric how will we determine the format of the date being printed in the string? For this specific use-case, we need a unix echo timestamp, but we may need others later.

[leian7]

@Kennric @ramereth For now I check for 'date' and insert the timestamp if 'date' is there. I interpreted "unix timestamp" as the regular "seconds since 1970" unix standard, is this correct?

leian@osuosl.org:Timestamp Test:1497398504:Annie Lei

[ramereth]

@leian7 yes, that is correct

[ramereth]

@Kennric can we please get this merged and deployed?